Excavation machines, such as wheel loaders, are used to load earthen material onto a haul truck for transportation away from a worksite. Some wheel loaders are articulated and also have steerable wheels, which can make efficient maneuvering of the machines difficult for a novice operator. In order to be profitable, the operator must move as much material as possible within a given period of time. Further, in order to reduce operating costs, the operator should control the machine to use as little fuel as possible and to reduce wear of the machine (e.g., to reduce tread wear of the machine's tires). During a typical truck loading cycle, the operator must fill a machine's bucket with material from a pile, back away from the pile while turning, reverse direction, and travel toward a waiting haul truck again while turning and also while lifting the bucket. The operator must then empty the bucket into the haul truck, back away from the haul truck while turning, reverse direction again, and travel towards the pile while turning and also while lowering the bucket. This can be difficult to do properly, especially if the operator is unskilled or inexperienced.
One attempt to improve excavation machine control is disclosed in U.S. Pat. No. 6,363,632 of Stentz et al. that issued on Apr. 2, 2002 (“the '632 patent”). Specifically, the '632 patent discloses an autonomous excavation system for use with a wheel loader. The system includes a left sensor, a right sensor, and a control module. Information from the two sensors is used by the control module to autonomously navigate the wheel loader during operation thereof. In addition, the sensors monitor the wheel loader's bucket to determine a loading status, as well as an area adjacent the bucket as the wheel loader backs away from or moves toward a soil face.
For example, as the wheel loader backs away, each sensor provides information concerning areas to the left and right of the wheel loader so that adequate response time is provided if an object obstructs the path of the wheel loader. Once the wheel loader reaches a pivot point, it reverses direction and stops as the bucket is raised to full height. During this period, information from the sensors is used to construct a range map of the soil face for use in planning the next excavation. After the bucket is fully raised, the sensors scan either side of the wheel loader as the wheel loader moves toward a dump truck. Information from the sensors is then used to monitor a clearance between the wheel loader and a bed of the dump truck. Once the bucket is unloaded, the sensors are again used to scan behind the wheel loader as it backs up to the pivot point, and the sensors continue to scan the area in front of the wheel loader as it approaches the soil face.
Additionally, upon arrival of the dump truck, the sensors are used to scan the dump truck, which provides information used by the control module to determine the location and orientation of the dump truck. As the material is moved from the soil face into the dump truck, the bucket of the wheel loader changes position and orientation. In addition, the dump trucks may vary in size, precise position, and orientation relative to the wheel loader. All such changes are taken into account to maximize efficiency in transferring the material with minimal spillage.
Although the system of the '632 patent may reduce operator burden by automating machine control, the system may still be less than optimal. In particular, the machine movements may not be optimally controlled to improve productivity, reduce fuel consumption, or reduce machine wear under varying worksite conditions. Further, the system of the '632 patent may be complex and expensive, and lack broad applicability to manned machines.
The disclosed excavation system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.